Multi-compartment phae separation tank for multiple reductant injectors

ABSTRACT

A cooling system in an aftertreatment unit for a multi-cylinder internal combustion engine is disclosed. The aftertreatment unit includes a selective catalyst reduction (SCR) module, an exhaust conduit portion, and a number of reductant injectors. Each reductant injector includes an injector coolant outlet. The cooling system supplies coolant to the reductant injectors by a coolant pump. A phase separation tank, positioned at a higher gravitational potential downstream of the reductant injectors, includes a number of compartments. Each compartment includes at least one inlet portion and at least one outlet portion. Each inlet portion is in fluid communication to the injector coolant outlet and each outlet portion is in fluid communication with the coolant reservoir. A coolant anti-siphon line portion facilitates fluid communication between the reductant injectors and the phase separation tank. Additionally, a coolant vent line facilitates fluid communication between the phase separation tank and the coolant reservoir.

TECHNICAL FIELD

The present disclosure relates generally to cooling circuits in an aftertreatment unit of a multi-cylinder, internal combustion engine. More specifically, the present disclosure relates to the use of a phase separation tank within the cooling circuit to cool a set of reductant injectors after a hot engine shutdown.

BACKGROUND

Aftertreatment units are commonly employed in internal combustion engines for treating exhaust gases. Such aftertreatment units generally include a selective catalyst reduction (SCR) module connected to an exhaust conduit portion or a mixing pipe, through which the exhaust gases flow. Reductant injectors are typically fluidly connected to the exhaust conduit portions to inject a reductant fluid into a passing stream of exhaust gas. A reductant fluid may typically include anhydrous ammonia, aqueous ammonia, or urea. Once the fluid reductants are injected into the mixing tube, a mixing is performed to treat the exhaust gas before an emission into the environment.

Fluid reductant injectors generally include injector tips, which are situated relatively close to the passage of the exhaust gas. In so doing, the reductant injector tips are subject to considerably high temperature conditions of the exhaust gas, which frequently deter the reductant injectors from injecting an optimal amount of reductant fluid. In general, injector life is adversely affected upon prolonged exposures to such temperature extremes (generally exceeding around 120° C.).

Coolant circuits are therefore employed within aftertreatment units to inhibit affects of such high temperatures on the injector tips. More specifically, reductant injectors have coolant jackets configured into their structure, and, more particularly, around the reductant injector tips, into which a coolant may enter to lower the temperatures within.

During a hot engine shutdown, a coolant flow to the reductant injectors may cease for a relatively prolonged period. In such a case, the tip of the reductant injector may continue to sustain the high temperatures of the exhaust conduit. Such temperatures may range between 30-40° C. above a bearable value, thus potentially shortening the life of the injector tip. For relatively large internal combustion engines with a multi-cylinder configuration, multiple fluid reductant injectors are generally arranged. Given the need to maintain efficient operability, such a configuration generally prescribes the requirement to cool each of the reductant injectors optimally and in a manner that promotes space efficiency.

U.S. Pat. No. 6,223,526 discloses a dual-compartment fuel storage tank where each compartment is configured to respectively store a fuel and a reducing agent. Although this reference apparently provides a means to reduce storage space for an application involving storage of dual fluids, no solution is provided to hold a coolant in cooling systems such as a cooling system for multiple reductant injectors, in a space efficient fashion. More particularly, no solution exists for tanks (such as phase separation tanks), that may temporarily store a coolant flow from a multi-injector reductant circuit, to optimally utilize an available space.

SUMMARY OF THE INVENTION

Various aspects of the present disclosure illustrate a cooling system in an aftertreatment unit for a multi-cylinder internal combustion engine. The aftertreatment unit includes a selective catalyst reduction (SCR) module, an exhaust conduit portion connected upstream to the SCR module, and a number of reductant injectors arranged in proximity to the exhaust conduit portion. Each reductant injector has an injector coolant outlet. Moreover, the reductant injectors are configured to inject a reductant fluid into the exhaust conduit portion. The cooling system includes a coolant circuit having a coolant reservoir. At least one coolant pump circulates a coolant through the coolant circuit, and facilitates a coolant flow from the coolant reservoir to the plurality of reductant injectors. A phase separation tank, positioned downstream of the reductant injectors, is deployed at a higher gravitational potential in relation to the reductant injectors. The phase separation tank includes a plurality of compartments, with each compartment having at least one inlet portion and at least one outlet portion. Each inlet portion is in fluid communication to at least one of the injector coolant outlets, and each outlet portion is in fluid communication with the coolant reservoir. Further, a coolant anti-siphon line portion facilitates the fluid communication between the plurality of reductant injectors and the phase separation tank. Moreover, a coolant vent line facilitates fluid communication between the phase separation tank and the coolant reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of cooling system applied in an aftertreatment unit of a multi-cylinder internal combustion engine, in accordance with the concepts of the present disclosure; and

FIG. 2 is an exemplary isometric view of a phase separation tank applied for the cooling system of FIG. 1, in accordance with the concepts of the present disclosure.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a block diagram of an exemplary aftertreatment unit 100 for treating exhaust gases from an internal combustion engine 102. The aftertreatment unit 100 works in conjunction with a cooling system 104. The aftertreatment unit 100 includes a diesel particulate filter (DPF) 106 and a selective catalyst reduction module (referred to as SCR 108) for the treatment of the exhaust gases prior to emission into the environment. An exhaust conduit 110 fluidly connects the DPF 106 to the SCR 108. The exhaust conduit 110 includes a mixing chamber, referred to as an exhaust conduit portion 112, which accommodates a number of fluid reductant injectors 114. A fluid reductant tank, referred to as a Diesel Emission Fluid (DEF) tank 116, is fluidly connected to the fluid reductant injectors 114. The DEF tank 116 holds a DEF 118.

The internal combustion engine 102 (hereinafter referred to as engine 102) may be a multi-cylinder engine configured to be employed in heavy machinery, mobile equipment, and related applications. For example, off-highway trucks, mining trucks, skid steer loaders, wheel loaders, track type tractors, excavators, dozers, wheel loaders, and/or the like. The present disclosure also envisions an extended application to stationary machines, such as power generation systems and other electric power generating machines. Although the present disclosure proposes the deployment of a multi-cylinder diesel engine, an equivalent application to other engine types is not ruled out.

As part of the aftertreatment unit 100, the DPF 106 may be selected from one of widely available DPF's in the market. The DPF 106 may be connected to the exhaust port 120 of the engine 102 and is configured to receive exhaust gas from the engine 102 in a raw, untreated state. Upon reception, the DPF 106 is configured to filter or separate soot or diesel particulate matter from the inflowing exhaust gas.

The exhaust conduit portion 112 is fluidly connected to the DPF 106 via the exhaust conduit 110 and is positioned downstream to the DPF 106 (or the exhaust gas flow, A). The exhaust conduit portion 112 may be shaped and structured as conventionally known and may be configured to receive a filtered exhaust gas from the DPF 106. The exhaust conduit portion 112 includes a mixing chamber, which typically facilitates a mixing of the filtered exhaust gases from the DPF 106 with a reductant fluid, such as the DEF 118. Although not limited, typical reductant fluids or DEFs may include anhydrous ammonia, aqueous ammonia, or urea.

The SCR 108 is fluidly connected further downstream to the exhaust conduit portion 112. The SCR 108 includes a catalyst, such as titanium oxide, and other active catalytic components of oxides of base metals to convert nitrogen oxides in the exhaust gases into diatomic nitrogen and water. Base metals may include, but are not limited to, vanadium, molybdenum, and/or tungsten. As with the DPF 106, the SCR 108 may also be chosen from among the widely known SCR units available in the art.

In generic multi-cylinder configurations, and relatively large engine applications, multiple fluid reductant injectors 114 are deployed. This is because emissions from relatively larger engines may require additional quantities of DEF 118 to neutralize the harmful constituents of the filtered exhaust gas. Accordingly, four fluid reductant injectors 114 are shown here. Variation in the number of fluid reductant injectors 114 may be contemplated. Correspondingly, the exhaust conduit portion 112 may include provisions for accommodating the fluid reductant injectors 114. The fluid reductant injectors 114 may be threadably engaged with the exhaust conduit portion 112, although other engagement measures are speculated. At one end, the fluid reductant injectors 114 are fluidly connected to the DEF tank 116 to receive a continuous supply of the DEF 118, via a set of conduit flow lines. In an embodiment, each fluid reductant injector 114 may include a dedicated DEF supply line. A continuous DEF supply may be facilitated by a DEF pump (not shown) and may include further connections that fluidly loop back to the DEF tank 116 to form a corresponding DEF circuit (not shown).

Although not limited, the fluid reductant injectors 114 may be arranged along a length of the exhaust conduit portion 112. The fluid reductant injectors 114 may be configured to inject a predetermined quantity of DEF 118, periodically, into the exhaust conduit portion 112. A DEF injection may be such that a fine atomized spray of DEF 118 is introduced into the exhaust conduit portion 112, to facilitate an effective mix of the DEF 118 with the incoming exhaust fumes.

The fluid reductant injectors 114 include injector tips 124 projected into the exhaust conduit portion 112. The injector tips 124 facilitate injection of a predetermined quantity of DEF 118 into the exhaust conduit portion 112, and, more particularly, into a stream of an inflowing exhaust gas. However, that arrangement subjects the injector tips 124 to high temperature conditions of the flowing exhaust gas. Because the injector tips 124 malfunction owing to those temperature conditions, repairs and replacement is generally sought.

Coolant jackets (not shown) are generally structured around the fluid reductant injectors 114, and, more particularly, around the injector tips 124. Such coolant jackets allow a coolant 122 from a cooling system, such as the cooling system 104, to flow into the coolant jackets within the fluid reductant injectors 114, receive heat from the injector tips 124, and reduce the temperature therein. Accordingly, each of the fluid reductant injectors 114 includes injector coolant inlets 126 and injector coolant outlets 128, for a respective inflow and outflow of the coolant 122.

Therefore, to downplay the affects of temperature, the fluid reductant injectors 114 are operably connected to the cooling system 104. The cooling system 104 includes a coolant circuit 130 that has a coolant reservoir 132, at least one coolant pump 134, a phase separation tank 136, a coolant anti-siphon line 138, and a coolant vent line 140.

The coolant reservoir 132 stores the coolant 122 and is fluidly connected to each of the fluid reductant injectors 114, as noted, via a coolant supply line 142. Supply lines that extend from the coolant reservoir 132 to a radiator (not shown) of the engine 102 may also be envisioned. The coolant pump 134 is connected to the coolant supply line 142 to facilitate a pressured supply of the coolant 122 from the coolant reservoir 132 to each of the fluid reductant injectors 114. Although not limited, the coolant pump 134 may be a positive displacement pump.

A coolant manifold tank 143 may be positioned downstream the coolant pump 134 to receive a pressurized coolant inflow from the coolant reservoir 132, through the coolant supply line 142. At an outlet of the coolant manifold tank 143, a number of coolant lines 145 (four in the disclosed embodiment) may be provided. The coolant lines 145 may extend and fluidly connect to each of the fluid reductant injectors 114. Such an arrangement facilitates a fluid communication link between the coolant manifold tank 143 and the fluid reductant injectors 114, in turn establishing fluid communication between the coolant reservoir 132 and fluid reductant injectors 114. An individual coolant outflow to each fluid reductant injectors 114 may be thus attained.

Injector coolant inlets 126 structured within the fluid reductant injectors 114 provide the coolant supply line 142 with an access for delivering coolant 122 into the fluid reductant injectors 114. In an embodiment, a coolant supply from the coolant reservoir 132 may be provided into a single conduit line, which splits into multiple lines to individually reach each of the fluid reductant injectors 114. Additionally, a coolant delivery based on a common-rail coolant supply system may be contemplated as well.

Injector coolant outlets 128 are provided within the fluid reductant injectors 114 in correspondence to each injector coolant inlet 126. The injector coolant outlets 128 facilitate an outflow/exit of the coolant into the coolant anti-siphon line 138. The coolant anti-siphon line 138 fluidly connects each of the injector coolant outlets 128 of the fluid reductant injectors 114 to the phase separation tank 136 (best seen in FIG. 2).

Notably, the coolant anti-siphon line 138 may be a relatively short line (such as shorter than about 12 inches), with a relatively wide cross-section (such as wider than about ¼ inches in interior diameter). Such a configuration provides minimal resistance to a backward coolant flow from the phase separation tank 136 to the fluid reductant injectors 114. The values noted here, however, need not be seen as limiting in any way. Further, each fluid reductant injector 114 may include provisions for having individual anti-siphon lines, as shown.

The phase separation tank 136 is positioned downstream of the fluid reductant injectors 114, along a direction, B of an operational coolant flow. In relation to the fluid reductant injectors 114, the phase separation tank 136 is positioned at a relatively higher gravitational potential in the coolant circuit 130. In so doing, a minimum amount of coolant 122 remains trapped in the cooling loop (a portion of the coolant anti-siphon line 138) during hot engine shutdowns, thereby maximizing a possibility of a reverse coolant movement caused by the head pressure.

As such, the phase separation tank 136 may act only as a temporary reservoir for the coolant 122 by imparting substantially negligible phase separation. Rather, a phase separation of the coolant 122 may be imparted by heat sinks (not shown), which may facilitate a coolant vaporization. Such vaporization of the coolant 122 generally results in the generation of a pressure head downstream of the fluid reductant injectors 114.

Further, the coolant vent line 140 fluidly connects the phase separation tank 136 back to the coolant reservoir 132 and completes the coolant circuit 130. The coolant vent line 140 is configured to purge the phase separation tank 136 of the used coolant back to the coolant reservoir 132. In a preferred embodiment, the coolant vent line 140 sustains a pressure head from a heat sink (not shown), which generates negative (or backflow) pressure. That negative pressure forces the coolant 122 in the phase separation tank 136 to flow backwards during a hot engine shutdown (discussed later). Though not explicitly shown, a coolant condensation process may be envisioned by having conduit lines extending from the phase separation tank 136 to a machine radiator, before having the coolant 122 delivered to the coolant reservoir 132.

Accordingly, an impact of the head pressure, created by the vaporization of the coolant 122, is facilitated via the coolant vent line 140, from a heat sink (not shown) to the phase separation tank 136. Optionally, a heat sink may be a regeneration system head (not shown) incorporated within the coolant circuit 130 where coolant vaporization and pressure build-up may occur.

Referring to FIG. 2, the phase separation tank 136 is shown in relatively greater detail. The phase separation tank 136 includes a number of compartments 202. In the depicted embodiment, the phase separation tank 136 includes four compartments 202, where each compartment 202 corresponds to each of the fluid reductant injectors 114. Options may be envisioned where the numbers of compartments 202 differ from what is disclosed. For example, a pair of fluid reductant injectors 114 may correspond to a single compartment 202. Accordingly, when four fluid reductant injectors (114) are employed, as shown, the phase separation tank 136 may include only two corresponding compartments 202. Other such configurations and arrangements may be contemplated. Accordingly, the structure of the phase separation tank 136 need not be viewed as restricting the spirit and scope of the disclosure in any way.

Each compartment 202 includes at least one inlet portion 204 and at least one outlet portion 206. Each inlet portion 204 is in fluid communication with at least one of the injector coolant outlets 128 of the fluid reductant injectors 114. Further, each outlet portion 206 of the phase separation tank 136 is fluidly connected to the coolant vent line 140, thereby facilitating fluid communication with the coolant reservoir 132. Notably, at least one outlet portion 206 corresponds to at least one inlet portion 204.

INDUSTRIAL APPLICABILITY

During an engine operation, the coolant temperature is preferably kept such that the coolant remains in a fluid state, with minimum vaporization. During a hot engine shutdown, however, the coolant pump 134 is shut off, or deactivated, leaving a significant amount of hot, but non-volatile coolant in proximity to a heat sink. In some embodiments, the heat sink may be a regeneration system head (not shown), as already noted. Other heat sinks, particularly those that remain substantially hot during a hot engine shutdown, may also be contemplated. The resulting heat generally causes the coolant 122 to vaporize, thereby producing a relatively small but significant head pressure downstream in the coolant circuit 130. The coolant vent line 140 sustains that vaporized coolant in a direction opposite (direction C) to the typical downstream operational flow. In effect, a vaporized coolant 144 enters the phase separation tank 136, causing negative head pressure in the phase separation tank 136.

This head pressure generally forces the coolant 122 (in the liquid state and at a lower temperature) in the phase separation tank 136, to flow backward through the coolant anti-siphon line 138 into each of the fluid reductant injectors 114. Such a phenomenon provides desired cooling to fluid reductant injectors 114, and, more particularly, to the injector tips 124 of the fluid reductant injectors 114, keeping them from malfunctioning and deformation. Adverse affects of heat may thus be avoided.

When utilizing the phase separation tank 136, placed relatively above the fluid reductant injectors 114, obtaining a relatively large amount of vaporized fluid to provide a sufficient head pressure may be avoided. That is because gravity adds to that head pressure, easing the liquid coolant flow from the phase separation tank 136 into the fluid reductant injectors 114, thereby causing temperature reductions of around 30-40° C. at the injector tips 124 in a relatively short period.

An alternative phenomenon that may occur after a hot engine shutdown is described below. Once the coolant pump 134 stops a coolant supply, a remaining coolant 122 within the fluid reductant injectors 114 vaporizes and rises through the coolant anti-siphon line 138 to reach the phase separation tank 136. Such a process forces the condensed coolant 122 within the phase separation tank 136 to flow back into the coolant anti-siphon line 138, in the direction C, opposite to the direction, B, and reach the fluid reductant injectors 114 by gravity feed, thereby cooling the fluid reductant injectors 114.

The use of injected DEF 118 may reduce or eliminate the need for exhaust gas recirculation (EGR). Therefore, DEF injecting systems are substantially indispensible components of an overall exhaust aftertreatment system. Accordingly, the use of the cooling system 104, for an injector tip (124) of a DEF injector system, is considerably valuable in extending the life of the injector tips 124, and, therefore, the overall efficiency of such systems. Moreover, by use of the multi-compartment phase separation tank 136, one may minimize the need to have bulky, space-consuming structures within the coolant circuit 130.

It should be understood that the above description is intended for illustrative purposes only and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure may be obtained from a study of the drawings, the disclosure, and the appended claim. 

What is claimed is:
 1. A cooling system in an aftertreatment unit for a multi-cylinder internal combustion engine, the aftertreatment unit including a selective catalyst reduction (SCR) module, an exhaust conduit portion connected upstream to the SCR module, and a plurality of reductant injectors in proximity to the exhaust conduit portion, wherein the plurality of reductant injectors is configured to inject a reductant fluid into the exhaust conduit portion, each reductant injector having an injector coolant outlet, the cooling system comprising: a coolant circuit having: a coolant reservoir; at least one coolant pump to circulate a coolant through the coolant circuit and facilitate a coolant flow from the coolant reservoir to the plurality of reductant injectors, and back to the coolant reservoir; a phase separation tank, positioned downstream of the plurality of reductant injectors, at a higher gravitational potential in relation to the plurality of reductant injectors, the phase separation tank including: a plurality of compartments, each compartment having at least one inlet portion and at least one outlet portion, wherein each inlet portion being in fluid communication to at least one of the injector coolant outlet and each outlet portion being in fluid communication with the coolant reservoir; a coolant anti-siphon line portion, facilitating the fluid communication between the plurality of reductant injectors and the phase separation tank; and a coolant vent line, facilitating the fluid communication between the phase separation tank and the coolant reservoir. 